In wheeled vehicles of all types, it is necessary to provide bearings for axles so that associated wheel hubs may rotate freely on the end of a relatively stationary axle. Such bearings must be lubricated and seals are required to retain the lubricating medium whether it be grease or oil. Frequently, wear sleeves are employed to prevent undue wear of the axle by the seals. Sometimes such wear sleeves have been separate elements and sometimes they have been an integral part of a unitized seal.
Until quite recently, such bearing, seal and wheel hub means have been assembled piece by piece. The bearing races have been fitted to designated axle portions and corresponding portions of the associated wheel hub. The bearing elements are usually spaced as far apart axially as possible with a tapered axle portion between the elements. The assembly also includes one or two seals, depending upon the particular design. These wheel hub assemblies have typically provided long lasting performance when assembled properly. However, such an assembly process requires skilled personnel and proper equipment to achieve proper installation and operation. If repair or replacement of any part becomes necessary, correct positioning and adjustment of all elements becomes even more of a challenge and damaged parts are a quite likely result. Typical prior art assemblies are illustrated in U.S. Pat. No. 4,552,367 assigned to Garlock Inc and U.S. Pat. No. 4,037,849 assigned to The Mechanex Corp.
More recently, some efforts have been made to develop assemblies which permit more of the various elements to be pre-assembled and adjusted, thus resulting in less dependance on the skills of the field mechanic. One such attempt has been the SAF Euro-axle developed by Otto Sauer Achsenfabric of Keilberg, Germany. These units accomplish much in terms of allowing factory assembly and adjustment of sealed bearing units and avoidance of so much dependance on the skills of the field mechanic. However, these units are not constructed to allow prefilling with oil which is a preferred bearing lubricant as compared to grease. More significantly, a special axle is included in the assembly and the pre-assembled units cannot be adapted to the millions of existing axles presently in service.
Another recent effort at development of pre-assembled and pre-adjusted sealed bearing units has been made by SKF Sweden. However, as with SAF units described previously, the SKF units are not adapted to prefilling with oil lubrication and they are not adaptable to the millions of existing axles. Furthermore, since the bearing units are more closely located relative to one another, there can be a tendency toward lessened wheel stability in operation.